Vacuum interrupter chambers are used in the low-voltage, medium-voltage and high-voltage range. The contact pieces are located within a vacuum, and the switching operation itself takes place under a vacuum atmosphere. During the switching process, in particular under short-circuit conditions, the aim is to extinguish the arc produced as quickly as possible. Said arc as such is a high-energy plasma flow which generates vaporization processes within the vacuum interrupter chamber. In order that no metallic layer is formed on the inside on the ceramic wall material of the vacuum interrupter chamber after a large number of switching operations, and therefore that the insulation capacity of the unit is reduced, shielding components made from metallic materials with relatively thin walls are generally introduced within the vacuum interrupter chamber and are arranged in the vicinity of the arc gap between the contact pieces and the insulation.
The metal vapor flowing away which is brought about by the switching operation then condenses on the surface of these shields. Furthermore, other high-energy plasma jets, which likewise come from the contact region, are also accommodated by the shield. As a result, the voltage-insulating function of the ceramic sleeve on the vacuum interrupter chamber inside is maintained. A high electrical field strength is present at the edges of these introduced shielding components, particularly under test conditions.
The plasma jets impinging on the shield heat it locally, with the result that material fusing and vaporization can occur. This can firstly increase the vapor pressure within the vacuum interrupter chamber during the switching operation and can secondly cause the shield to fuse completely. Particular loading of the shield occurs in the case of a compact design of the vacuum interrupter chamber with frequent switching of short-circuit currents.
The high erosion strength required cannot be achieved by the conventionally used shielding materials in this form, however, or can only be achieved incompletely.